Your versions seems to be the proper ones from the 5.9.0 release.
I have tried to setup a new instance with that code, created a page and tried to delete and everything was ok. What kind of page were you trying to remove? Was it already on the system or was created fresh since after upgrade?
Please try to create a new one and remove it as I did, if it works the problem could have to do with the page itself (different format? we would have to see)
Ciao
Antonio
